Betaine Catalysis for Hierarchical Reduction of CO 2 with Amines and Hydrosilane To Form Formamides, Aminals, and Methylamines

An efficient, sustainable organocatalyst, glycine betaine, was developed for the reductive functionalization of CO 2 with amines and diphenylsilane. Methylamines and formamides were obtained in high yield by tuning the CO 2 pressure and reaction temperature. Based on identification of the key intermediate, that is, the aminal, an alternative mechanism for methylation involving the C 0 silyl acetal and aminal is proposed. Furthermore, reducing the CO 2 amount afforded aminals with high yield and selectivity. Therefore, betaine catalysis affords products with a diversified energy content that is, formamides, aminals and methylamines, by hierarchical two‐, four‐ and six‐electron reduction, respectively, of CO 2 coupled with C−N bond formation.